I chose the fastback over the coupe simply on looks alone. I had my heart set on that body style for YEARS and I knew that if I bought a coupe for price or practicality reasons then deep down I'd regret it and wish that I'd gone with a fastback instead.
But now that I own a fastback I can tell you that the downsides are...
1. A miniscule boot
2. A miniscule back seat area.
3. Significantly more expensive than a coupe in the same condition.
My advice? If you're as undecided as you appear to be and either style appeals equally to you then go for the coupe. You'll save some dollars and get a more practical car. But if you love the fastback styling like I did then don't settle for anything else. I definitely don't regret buying an expensive car with a tiny boot!!